Although there have been remarkable advances in the analysis of human chromosome sequences thanks to the progress in human genome research, this does not mean that all the human genetic functions have been clarified. In humans, gene diversity is significantly associated with changes in gene functions. In fact, it is known that in humans, a plurality of mRNAs are transcribed from a particular region of a chromosome to produce different variants.
For the series of genes that have been discovered by the present inventors, and that can be used as biomarkers specific for the brain/nerves or specific for nerve differentiation (abbreviated as “brain/nerve-specific genes” or “brain/nerve-specific genes 1 to 10” as required), known variants have been reported. Examples of such known variants include known variants of brain/nerve-specific gene 1 (Genbank accession number: NM—133460.1; non-patent documents 1 and 2), brain/nerve-specific gene 2 (Genbank accession number: NM—005163.1; non-patent documents 3 and 4), brain/nerve-specific gene 3 (Genbank accession number: NM—181784.1; non-patent documents 5 and 6), brain/nerve-specific gene 4 (Genbank accession number: NM—003930.3; non-patent documents 7 and 8), brain/nerve-specific gene 5 (Genbank accession number: NM—000898.3; non-patent documents 9 and 10), brain/nerve-specific gene 6 (Genbank accession number: NM—005079.1; non-patent documents 11 and 12), brain/nerve-specific gene 7 (Genbank accession number: NM—001679.2; non-patent document 13 and 14), brain/nerve-specific gene 8 (Genbank accession number: NM—000431.1; non-patent documents 15 and 16), brain/nerve-specific gene 9 (Genbank accession number: NM—153449.2; non-patent document 17), and brain/nerve-specific gene 10 (Genbank accession number: NM—015009.1; non-patent documents 18 and 19).
However, it is not known that the brain/nerve-specific genes 1 to 10 can be useful as biomarkers specific for the brain/nerves or specific for nerve cell differentiation, and that the particular variants discovered by the present inventors exist in the brain/nerve-specific genes 1 to 10.    [Non-patent document 1] Ota, T. et al., Nat. Genet. 36 (1), 40-45 (2004)    [Non-patent document 2] Strausberg, R. L. et al., Proc. Natl. Acad. Sci. U.S.A. 99 (26), 16899-16903 (2002)    [Non-patent document 3] Staal, S. P., Proc. Natl. Acad. Sci. U.S.A. 84 (14), 5034-5037 (1987)    [Non-patent document 4] Staal, S. P. et al., Genomics 2 (1), 96-98 (1988)    [Non-patent document 5] Wakioka, T. et al., Nature 412 (6847), 647-651 (2001)    [Non-patent document 6] Kato, R. et al., Biochem. Biophys. Res. Commun. 302 (4), 767-772 (2003)    [Non-patent document 7] Marie-Cardine, A. et al., FEES Lett. 435 (1), 55-60 (1998)    [Non-patent document 8] Kouroku, Y. et al., Biochem. Biophys. Res. Commun. 252 (3), 738-742 (1998)    [Non-patent document 9] Kochersperger, L. M. et al., J. Neurosci. Res. 16 (4), 601-616 (1986)    [Non-patent document 10] Bach, A. W. et al., Proc. Natl. Acad. Sci. U.S.A. 85 (13), 4934-4938 (1988)    [Non-patent document 11] Chen, S. L. et al., Oncogene 12 (4), 741-751 (1996)    [Non-patent document 12] Byrne, J. A. et al., Genomics 35 (3), 523-532 (1996)    [Non-patent document 13] Lingrel, J. B. et al., Prog. Nucleic Acid Res. Mol. Biol. 38, 37-89 (1990)    [Non-patent document 14] Malik, N. et al., J. Biol. Chem. 271 (37), 22754-22758 (1996)    [Non-patent document 15] Kopito, R. R. et al., Proc. Natl. Acad. Sci. U.S.A. 77 (10), 5738-5740 (1980)    [Non-patent document 16] Schafer, B. L. et al., J. Biol. Chem. 267 (19), 13229-13238 (1992)    [Non-patent document 17] Wu, X. et al., Genomics 80 (6), 553-557 (2002)    [Non-patent document 18] Bach, I. et al., Nat. Genet. 22 (4), 394-399 (1999)    [Non-patent document 19] Katoh, M. et al., Int. J. Mol. Med. 13 (4), 607-613 (2004)